Electronic versus thermal response for nonlinear prism coupling

Numerical studies of nonlinear prism coupling into thin-film organic material waveguides have been carried out. Results are presented showing that, for an undiluted, low absorption material, the electronic response dominates at pulse widths of tens of nanoseconds. The result of an increase in the absorption is that shorter pulses are necessary for access to the Kerr law nonlinearity alone. Guidelines are provided for distinguishing between electronic and thermal responses.